The present invention relates to a pressure pulse generator that comprises a circuit filled with pressure fluid, and at least one communication channel that is connected to the circuit and via which the pressure fluid can flow into and out of the circuit. The invention also relates to a pressure pulse generator element and a method of controlling the pressure pulse generator, as well as use of the pressure pulse generator for operating a valve in an internal combustion engine.
The invention is applicable to all types of technical areas in which pressure pulses are to be generated. In particular, it is applicable to applications that poses high requirements on the speed with which the pulses can be generated and on the duration period of the individual pulses.
Internal combustion engines define such a field in which pressure pulses can be used in order to control and operate the movement of the valves of the combustion engine instead of operating and controlling the valve movements by means of a conventional transmission of the piston movement of the engine to the valves via a cam shaft.
Therefore, the invention will be described by way of example, but not in a delimiting way, with reference to the application in which it is used for controlling and operating the valves to the combustion chamber of a combustion engine.
Since many years, the designers of internal combustion engines have seen a need of being able to vary the valve periods during the operation of the engine, as this would result in great advantages with respect to, amongst others, fuel economy and emissions.
Therefore, extensive efforts have been made in order to replace conventional cam shaft systems for the opening and closing of engine valves by systems that are based on the use of electromagnetism for controlling and operating the valves of the engine. The disadvantage of such solution is that the high requirements on the speed by which the valves can be operated will result in high requirements on the electromagnets that are used. The mass that each electromagnet has to bring into motion corresponds to the mass of the valve. The valve must comprise a suitable magnetic material in order to be displaced by the action of one or more electromagnets, and such materials contribute to an increase of the mass of conventional valves. This often results in a evil circle in which an improvement of the valve from a magnetic point of view will result in a weight increase that, in its turn, results in a need of larger and more powerful electromagnets. Accordingly, in this way, it will be difficult to achieve an economically and practically good solution to the problem of obtaining a sufficiently fast control and operation of the valves of the engine. Moreover, it is well known that electromagnets will require a certain time for magnetizing and demagnetizing.
There are also efforts being made to obtain the requested movements of the engine valves by means of hydraulics. Today, such systems are tested by, amongst others, vehicle manufacturers. The pressure fluid, here the hydraulic liquid, is in this case used in order to effect the engine valve movement. Thereby, it is required that the pressure pulse generator that is used has an ability to deliver the pressure pulses that cause the valve movements rapidly and with high precision. The present inventor does not know any pressure pulse generator according to prior art that has the performance required to satisfyingly cope with the valve control at the rotations per minute of the engine that is used today in two-stroke and, in particular, four-stroke combustion engines. An obstacle to the accomplishing of such a pressure pulse generator may be the difficulty to achieve sufficiently rapid opening/closing movement of the valve or valves that is/are required in such a pressure pulse generator. Here, it should be mentioned that valves are often replaced by ports in modern two-stroke engine constructions, but that the present invention results in the possibility of using valve technology in two-stroke engines in a way corresponding to that of four-stroke engines.
In this context, it should also be mentioned that the pressure pulse generators that may come in question should be compact and occupy only a small space in combustion engine applications.
An object of the present invention is to provide a pressure pulse generator that is able to deliver pressure pulses of short duration and of variable length with high time precision and rapidity in order to effect any object. A further object is to provide a method that makes it possible to deliver pressure pulses with high time precision and rapidity.
A further object of the invention is to provide a pressure pulse generator element that can be used in a pressure pulse generator in order to make it easier for the latter to deliver short pressure pulses of variable length with high time precision and rapidity.
The object of the invention is achieved by means of a pressure pulse generator of the initially defined type that is characterized in that it comprises a first pair and a second pair of electronically controlled valves that are connected in series, and that the first pair of valves is arranged in said circuit upstream the at least one communication channel, and that the second pair of valves is arranged in said circuit downstream the at least one communication channel.
As the valves of the pair of valves are electrically controlled, the opening and closing of the valves can be controlled with high precision. The movements of the valves included in a pair of valves can be coordinated in such a way that they occur somewhat displaced in time, whereby reduced opening/closing times can be obtained.
The valves of the pressure pulse generator are preferably slide valves arranged to be displaced cross-wise a channel in the pressure fluid circuit that they are provided to close or open for passage of the pressure fluid. The valves of the pair of valves are, preferably, electromagnetically controlled, as such valves have the advantage of being able to operate both with high speed and precision.
According to a preferred embodiment the valves of each pair of valves are interconnected by two separate, parallel channels that lead from a first valve of the pair of valves to a second valve of the pair of valves, each valve being arranged to execute a closing or opening of each channel. This construction promotes a further refined control of the opening and closing of each individual pair of valves in a way that will be described more in detail later.
The valves of the pair of valves are arranged to occupy a first position in which they close a first channel of said channels and open a second one of said channels, and a second position in which they open the first channel and close the second channel. In order to make the pair of valves able to close, the first valve of each respective pair of valves is arranged to move towards and occupy its first position at the same time as the second valve moves towards and occupies its second position. Preferably, the channels are branches of a single pressure fluid conduit in the pressure fluid circuit, said branches being arranged upstream and downstream each individual pair of valves. However, it should be realised that a large number of alternative embodiments of the very pressure fluid circuit and the conduit system included therein are within the scope of the invention.
According to the invention, the pressure pulse generator comprises means for controlling the transition of the valves between their first and second positions, said control means being arranged to mutually displace, in time, the transition between the first and second position for the valves of the respective pair of valves. By means of a displacement in time of the activation of the movement of the valves included in a pair of valves between their respective positions, the time during which it is possible to keep any one of the two channels that connect the valves open for pressure fluid passage in connection to the change of the positions of the two valves can be varied.
Preferably, the control means comprise an electronic device arranged to control the activation or deactivation of one or more electromagnets for the purpose of affecting and moving the valves of the pair of valves, i.e. the valve bodies (slides), between their closing and opening positions, respectively. Preferably, the control means may be arranged to receive input from, for instance, sensors or the like and adjust the time displacement based on such input. The means may also comprise a program sequence in a computer program for controlling and emitting control signals to the valves of the pressure pulse generator, or, more precisely, to the electromagnets that operate the movements of the valves.
According to a preferred embodiment, the pressure pulse generator also comprises a cylinder unit and a piston that is displaceably arranged in the cylinder unit, said at least one communication channel being connected to the cylinder unit in such a way that the pressure fluid in the circuit can flow into and out of the interior of the cylinder through said communication channel in order to accomplish a displacement of the piston in the cylinder unit. A piston return means, for example, compression spring, is preferably provided in order to apply a pressure on the piston in a direction opposite to the one in which the piston is displaced when a pressure pulse is generated as a pressure fluid with a higher pressure is permitted to pass the first, upstream pair of valves. The piston return means is permitted to contribute to a return of the piston to a start position by letting the second, downstream pair of valves be opened for pressure fluid passage during a sequence following the flow sequence described above. The movement of the piston can, in its turn, be used for controlling or operating any mechanical device.
According to one embodiment, the piston is connected to a valve of a combustion engine and the movement of the piston is transmitted to an opening or closing movement of the valve of the combustion engine. The control means mentioned above thereby preferably control the activation and deactivation of said electromagnets based on the position of a crank shaft of the combustion engine.
The invention also relates to the initially defined method for controlling a pressure pulse generator, said method being characterized in that it comprises:
controlling, by means of electrical signals, the valves of a first pair and a second pair of valves that are connected in series, according to a certain sequence,
the first pair of valves being arranged in said circuit upstream the at least one communication channel, and
said second pair of valves being arranged in said circuit downstream the at least one communication channel.
The fact that the valves are arranged in pairs and that the opening and closing of the individual valves is performed in accordance with a predetermined sequence may be taken advantage of in order to shorten the time required for the opening and subsequent closing of a pair of valves for the passage of a pulse of the pressure fluid, as in comparison to when only individual valves are arranged instead of said pair of valves. Preferably, the pair of valves comprise two active valves or valve bodies that are moved in opposite directions in order to simultaneously, during a short moment, permit passage of a pressure fluid through one or more parallel channels that form the portion of the pressure fluid circuit conduit where the valves are arranged.
The valves of the first pair of valves are controlled, during a first period, to open for a flow of the pressure fluid in a direction out of the circuit through the communication channel, while at least one of the valves of the second pair of valves is kept closed in order to prevent fluid from passing the second pair of valves. During a second period, the valves of the second pair of valves are opened for permitting a flow of the pressure fluid back to the circuit via the communication channel and to pass at least one of these valves, while at the same time at least one of the valves of the first pair of valves is kept closed in order to prevent fluid from passing the first pair of valves. In that way, a pressure pulse is permitted to affect any object or any mechanical device to perform a back and forth movement.
The valves of each pair of valves are connected by two separate, parallel channels that lead from a first valve of the pair of valves to the second valve of the pair of valves, and a first one of the pair of valves is opened for passage of fluid through a first one of these channels and closed for passage of fluid in the second channel while, at the same time, the second valve is opened for fluid passage in the second channel but is kept closed for preventing passage of fluid in the first channel. The change of the positions of the two valves is preferably controlled in such a way that the valves, simultaneously during a short period, hold one of the two channels open for passage of the pressure fluid. As the valves, preferably electromagnetically controlled slide valves, thereby move in opposite directions, said period can be made very short.
During the change of the position of the respective valves of the pair of valves, the moment at which an electrical signal is given for activation of a first electromagnet, that operates a displacement of the first one of the valves, is controlled in relation to the moment at which a second electrical signal is emitted for activation of a second electromagnet that operates a displacement of the second valve, based on the requested length of time of the pressure fluid pulse that is thereby generated via the open channel.
The invention also relates to a pressure pulse generator, comprising a pair of valves that comprises a first valve and a second valve, characterized in that the first valves and the second valves are connected by means of two parallel channels that lead from a first valve of the pair of valves to a second valve of the pair of valves, and that each valve is arranged to execute a closing or opening of each channel. Preferably, the pressure pulse generator element has the features that have been described above for each one of the pair of valves included in the pressure pulse generator, and is preferably controlled in any of the ways that have been described above for said pair of valves.
Further features and advantages of the invention will be seen in the following detailed description and in the enclosed patent claims.